Process for treating revolving furnace flue gas dedusting water from steel mill by low hardness method

Abstract

The invention relates to a technology for treating steel mill converter gas dedusting water by adopting a low hardness method, which has the steps: wastewater from a converter gas washing tower enters an elevated tank, and an inorganic coagulant is added to the water body inside the elevated tank; an outlet of the elevated tank passes through a coarse granule separating machine which then recovers the coarse granule; the effluent of the coarse granule separating machine enters a slant plate sedimentation tank; an organic coagulant and a calcium reducing agent are added to the water body in the slant plate sedimentation tank; the sludge in the slant plate sedimentation tank is dewatered and reused; the effluent of the slant plate sedimentation tank enters a hot pond; an efficient sale-inhibition dispersion agent is added to the water body in the hot pond; and finally, the effluent of the hot pond is cooled by a cooling tower, enters a water cooling pond and is recycled to the converter gas washing tower for use. The technology has the advantages of improving water treatment efficiency, reducing water treatment cost, improving the cyclic utilization rate of the wastewater to 98 percent, ensuring zero wastewater efflux of the entire system and reducing water consumption per ton steel and wastewater discharge per ton steel, thus realizing the clean production of steel enterprises.

Description

【Technical field】 [0001] The invention belongs to the technical field of water treatment in steelworks, and relates to a process for purifying and cooling converter flue gas by a wet dedusting process, and chemically treating dust-removing waste water by a low-hardness method for treating converter flue gas dedusting water in steel mills. 【Background technique】 [0002] The main water used by iron and steel enterprises is the circulating water system, which is characterized by large water volume, high temperature, prone to corrosion and scaling, and has high requirements for water quality and water treatment technology. At present, the main problems in the treatment of steelmaking production wastewater are: the stability of the water quality of converter steelmaking flue gas dedusting wastewater is low, the total circulation rate of flue gas dedusting wastewater generally only reaches 40-60%, and some of them cannot be recycled at all and are discharged directly. Not only wa...

AI Technical Summary

Problems solved by technology

At present, the main problems in the treatment of steelmaking production wastewater are: the stability of the water quality of converter steelmaking flue gas dedusting wastewater is low, the total circulation rate of flue gas dedusting wastewater generally only reaches 40-60%, and some of them cannot be recycled at all and are discharged directly. Not only waste of resources, but also cause serious damage to the environment

[0009] (4) Wastewater sedimentation characteristics: The particle size of suspended solids in unburned flue gas purification wastewater is relatively large, and it is relatively easy to precipitate. The characteristics also change accordingly, which adversely affects the sedimentation of wastewater

[0011] (1) Scaling at the throat of the first and second texts affects the dust removal and cooling effect of the flue gas, especially the scaling of the heavy hammer that adjusts the air volume, which cannot operate normally, causing gas to overflow from the furnace mouth, and the flue gas emission is not up to standard and other hazards

[0012] (2) Scale deposits in the first bend, second bend and water seal affect ventilation and water flow, destroy the balance of the system, aggravate the scaling at the throat, and cause a vicious circle

[0013] (3) Scaling of return pipes, water supply pipes, and water pumps reduces water flow, affects dust removal efficiency and system balance, and affects production in severe cases

[0014] (4) The surface of the impeller of the induced draft fan is seriously fouled, which accelerates the wear of the impeller of the fan and affects the stability of production in severe cases

[0015] (5) Affect the secondary dust removal device

But in this way, the area and space of the sedimentation tank will be greatly increased, the utilization rate is low, and the cost is expensive. At the same time, the dehydration performance of the sludge is very poor. Most of the new steelmaking plants are designed with a hydraulic retention time of 1 to 1.5 hours. Steelworks with extended or increased capacity have hydraulic retention times of even less than 45 minutes

[0019] In order to prevent fouling and clogging of pipes in the circulating water system, especially to avoid clogging of the Venturi tube resulting in poor dust removal effect and even production accidents, various steelmaking plants use calcium reducing agents and add scale inhibitors and dispersants. The converter dedusting wastewater treatment process such as figure 2 As shown, the scale inhibitors and dispersants currently on the market are mostly polycarboxylates, and the scale inhibition effect is average under alkaline conditions, and the heat resistance effect is not good, and it is easy to lose its effect under the action of high temperature furnace gas. Lack of coordination with calcium reducing agents, the problem of pipeline blockage in various steelmaking plants is still prominent

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